The present invention relates to a system and method of measuring characteristics of an engine, and more particularly to an engine testing system (so-called engine bench system) for measuring various characteristics of an engine by directly connecting the engine with a dynamometer functioning as a driving power absorber and to a method of measuring the engine characteristics.
Generally, an engine testing system is constructed by connecting a dynamometer with a combination of an engine and a transmission. The control of the engine is executed by controlling a throttle opening of the engine, and the control of the dynamometer is executed by controlling a speed and a torque on the basis of detection signals detected by a speed detector and a torque detector provided in the dynamometer. This control is executed by PID control (Proportional, Integral and Derivative Control) using a controller.
However, such an engine testing system using the PID control has a possibility that the shaft connecting the dynamometer and the engine may cause resonance vibration due to a pulsation torque generated by the engine. Therefore, it is necessary to execute the PID control of the dynamometer within an engine operation range where a frequency of a pulsation vibration generated by the engine is smaller than a resonance frequency of a mechanical system of the dynamometer, the shaft, and the engine. Therefore, it is difficult to execute the speed control and the axial torque control in high-responsibility under this limitation by the mechanical system resonance frequency.
Although it is possible to design the mechanical system using a high rigidity shaft so that the resonance frequency of the mechanical system becomes out of an operation range of the engine, a torque control using the PID control has a limitation that uncertain factors such as an engine pulsation torque affects the control response of the torque control.
It is therefore an object of the present invention to provide a system and method which is capable of stably measuring engine characteristics in high speed by constructing a torque control system of the system via the structured-singular-value synthesis method.
An aspect of the present invention resides in a system for measuring characteristics of an engine. The system is constructed by connecting the engine with a dynamometer via a shaft. The system comprises a torque control system which controls at least one of an axial torque of the shaft and an engine load torque. The torque control system comprises a first block represented by a mechanical transfer function, a second block represented by an electric transfer function, and a torque controller. The first block receives an engine torque and a current and outputs an engine speed, the axial torque and a dynamo speed. The second block receives a command current and outputs the current. The torque controller receives one of a command axial torque and a command engine load torque, and at least one of the engine speed, the dynamo speed, and the axial torque and outputs the command current. The torque controller is represented by a transfer function which is designed using the structured singular value synthesis method so as to be adapted to the mechanical transfer function and the electric transfer function.
Another aspect of the present invention resides in a method for measuring characteristics of an engine using a torque control system for controlling at least one of an axial torque and an engine load torque in a system of the engine, the dynamometer, and the shaft. The method comprises the steps of: receiving an engine torque and a current and outputting an engine speed, the axial torque and a dynamo speed; receiving a command current and outputting the current; and receiving one of a command axial torque and a command engine load torque, and at least one of the engine speed, the dynamo speed, and the axial torque and outputting the command current, by means of a torque controller which is represented by a transfer function designed using the structured singular value synthesis method so as to be adapted to the mechanical transfer function and the electric transfer function.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.